The present invention generally concerns bearing assemblies. More particularly, the invention relates to a bearing assembly having an improved lubrication system to prevent lubricant loss between a bearing chamber and a bearing housing.
Bearing assemblies are typically designed having an inner and an outer ring, each defining an annular raceway situated in opposition to one another. Bearing elements are disposed in a bearing chamber defined between the opposed raceways, thereby permitting the rotational displacement of the inner and outer rings with respect to one another. To facilitate this relative rotation, such bearing assemblies are generally configured so that a lubricant may occasionally be conducted to the bearing chamber.
In a typical configuration, the inner and outer rings are secured within a housing. As such, the lubricant must be introduced into the bearing assembly from an external point through or around the housing. The lubricant travels to the bearing chamber by way of a lubrication path defined within the bearing group, which may comprise the inner and outer rings, the bearing elements, seals and other related elements generally secured by or within the housing. One general bearing construction also defines a second lubrication path extending through the housing to the first lubrication path. This second path allows lubricant to be conducted under pressure into the first lubrication path from a lubricant source.
A difficulty may often be encountered if such an arrangement is employed in, for example, an expansion bearing. In an expansion bearing, the clearance between the housing and the bearing group is sufficient to permit the bearing group to slide axially with respect to the housing. This axial movement may be desirable if relatively small axial shifts in shaft position are expected during operation. The looseness of the expansion bearing design, however, may allow lubricant to excessively leak from the bearing assembly during use. Specifically, contaminants within the bearing chamber or the first lubrication path may hinder lubricant flow, thus forcing lubricant through the clearance between the housing and the bearing group.
Often, an expansion pillow block bearing assembly includes an outer ring assembly comprising an outer ring and an aligning ring. The outer ring defines the outer raceway while the aligning ring positions the outer ring with respect to the housing. The aligning ring usually has an axially curved inner surface to receive a complementary outer surface of the outer ring. The aligning ring's outer surface is typically cylindrical to permit the aligning ring to move axially as described above.
The curved fit between the aligning ring and the outer ring is a tight fit that allows slight angular adjustments which may be necessary to compensate for angular misalignment of the shaft. The slip fit between the aligning ring and the housing permits relatively greater movement of the aligning ring relative to the housing than is permitted by the fit between the outer ring and the aligning ring. The aligning ring thus secures the bearing group while permitting some desirable axial movement.
In such a configuration, the first and second lubrication paths may respectfully define passageways through the aligning and outer rings and through the housing. Thus, the meeting of these passageways is at the slip fit between the aligning ring and the housing. Because of the relatively large clearance of this slip fit, however, lubricant conducted under pressure into the housing passageway may tend to leak between the aligning ring and the housing, particularly when contaminants in the bearing group or the bearing chamber impede lubricant flow.
One solution to this problem utilizes housing seals to reduce leaks from between the housing and the bearing group. Such housing seals may extend between the housing and the inner ring, defining a cavity open to the bearing chamber into which lubricant may be conducted. Often, however, seals do not adequately prevent leaks between the aligning ring and the housing. Additionally, the seals may themselves leak due to the relatively light contact between the seals and rotating elements of the bearing.